1. Field of the Invention
This invention relates to a method for processing a photographic silver halide photosensitive material which is simply referred to as photosensitive material hereinafter, and an automatic processor used therein.
2. Prior Art
Currently, most photographic silver halide photosensitive materials are processed using automatic developing machines or processors. Although a variety of processors are available, the processor to which the present invention pertains has a series of development, fixation, washing and drying functions.
The recent trend in the art is toward rapid processing of photosensitive material. For graphic art photosensitive materials, X-ray photosensitive materials, scanner photosensitive materials, and CRT image recording photosensitive materials, for example, there is an increasing need for rapid processing.
From the standpoint of environment protection, it is desired to reduce the amounts of processing solutions (including developer and fixer solutions) used in the processing of photosensitive material for reducing waste liquid disposal loads. The amounts of replenisher solutions to be replenished with the progress of photosensitive material processing must be reduced before the amount of waste liquid can be reduced. However, as processing becomes rapid and as the volume of fixer replenished is reduced, the fixation step becomes lower in fixing ability, resulting in insufficient desilvering of silver halide in unexposed areas and retention of more thiosulfate from the fixer solution in the photosensitive material which thus loses image stability on storage. Additionally, the sensitizing dye is not fully dissolved out of the photosensitive material, leaving unnecessary color (or residual color) in the processed photosensitive material.
In processing X-ray sensitive material, a developer containing an aldehyde hardener is often used in combination with a fixer containing an aluminum salt hardener as described in Japanese Patent Application Kokai (JP-A) No. 158439/1989. Since the aluminum salt hardener is more effective for hardening with lower pH levels, the working fixer solution is conventionally maintained at pH 4.0-4.5 by adjusting the pH of fixer solution and replenisher and by controlling the replenishment rate. The fixer at such low pH, however, can give off sulfur dioxide gas and acetic acid gas, producing unpleasant odor and causing corrosion of the processor and surrounding equipment. This is not desirable for the working environment since current processors are often installed in ordinary rooms rather than in special rooms.
Under the circumstance, the applicant proposed in JP-A 168741/1991 to process with a fixer which would provide a running equilibrium solution at pH 4.6 or higher. Although this method improves or eliminates the odor problem, the fixer is low in hardening effect, which leads to increased drying loads, often resulting in uneven drying or drying marks.
In view of the preparation (formulation) of developer and fixer concentrates as well as the preparation (dilution) of concentrates into working solutions, the processing solutions of one part composition are more advantageous than those of two or more part composition. Since the one part composition requires only dilution to form a working solution, the processor can be equipped with an automatic solution preparation system (for example, FCR-7000 system CR-LP-414, manufactured by Fuji Photo-Film Co., Ltd.).
In order that the developer concentrate be of one part composition, dialdehyde hardeners should be avoided since they are less stable in alkaline solution. In order that the fixer concentrate be of one part composition, it should be at pH 4.6 or higher for maintaining thiosulfates stable. Then the processing solutions provide little or no contribution to hardening and accordingly, photosensitive material should originally be increased in film strength. Increasing the film strength of photosensitive material is favorable for drying, but not for rapid processing because development, fixation and washing are all retarded. This means that the film strength of photosensitive material is limited and then, the above-mentioned feature of the processing system is retained, but drying loads are increased, often resulting in drying defects.
As previously mentioned, it is desired to reduce the replenishment volume. As the replenishment volume of fixer is reduced, the proportion of developer carried into the fixing bath from the developing bath is increased. The working fixer solution is thus increased in pH and the above-mentioned processing system must accommodate for increased drying loads.
Moreover, a demand for more rapid processing of photosensitive material requires that the overall processing time or dry-to-dry processing time be reduced from conventional 90 seconds to about 60 or 45 seconds. Then the drying time must be reduced while the drying capacity must be increased.
With the foregoing facts taken into account, it is generally desired to increase the drying capacity. One approach is to extend the drying zone, but not recommended because both the size and cost of the processor are increased. Other approaches for increasing the drying capacity are to increase the heater capacity and the air flow rate in the drying section, both of which can be implemented to some extent although a certain energy limit exists. It is also possible to use far-infrared heaters as disclosed in JP-A 234849/1989 and 118840/1989. Blower means for injecting hot air against photosensitive material surface is disclosed in JP-A 123236/1989 and 265855/1991. The drying capacity can be maximized by properly selecting the configuration of the blower means and the spacing thereof to the photosensitive material.
All these approaches are successful in increasing the drying capacity to some extent and leave little or no drying marks in the conventional 90-second process. However, in more rapid 60 or 45-second processes, drying marks can be left. Because of the increased drying capacity, such drying marks occur in certain intervals or cycles and varying degrees of drying appear as variations in image reflection density.